Various vehicles, such as aircraft and space craft, carry a substantial quantity of high power electronic devices that produce substantial quantities of heat. Although the amount of heat produced by each electronics device typically varies from application to application, increasing packaging densities, and hence increased heat production, has made thermal management an increasingly critical design consideration. In order to protect the devices and to ensure their proper operation, it is necessary that some form of device cooler be provided.
One manner of cooling such electronics devices is to circulate a coolant medium past the device such that the heat load is transferred to the coolant medium. The coolant medium is then circulated to another location where the heat is removed from the medium. Typically, such a cooling operation can be effected without changing the phase of the coolant. However, as is well known, heat exchange capacity of a given coolant medium can be substantially increased when the coolant medium undergoes a phase change, such as, for example, from the liquid phase to the vapor phase.
While many cooling systems have been proposed for cooling various heat producing devices using a vaporizable or an evaporative coolant medium, most cooling systems are not suitable for use in unusual gravitational conditions such as those encountered by spacecraft or high performance aircraft. For example, in the case of zero gravity conditions, a coolant medium in its liquid phase may lose contact with one or more of the heat transfer surfaces provided within the cooling device, thus severely degrading the performance of the cooling device. On the other hand, in the case of high performance aircraft high gravitational forces encountered during high "G" turns and other acrobatic maneuvers can propel a purely liquid coolant medium against only certain portions of the heat transfer surfaces and separate the coolant medium from the remaining heat transfer surfaces. Again, the performance of the cooling system is seriously degraded.
A variety of cooling devices are known in the art. For example, U.S. Pat. No. 4,494,171 issued to Bland et al., which is assigned to the assignee of the instant application, discloses a high efficiency cooling apparatus that uses jet impingement of coolant. Other patents, such as U.S. Pat. No. 4,559,580 issued to Lutfy, U.S. Pat. No. 4,962,444 issued to Niggemann, U.S. Pat. No. 5,016,707 issued to Nguyen, U.S. Pat. No. 5,025,856 issued VanDyke, et al., U.S. Pat. No. 5,029,640 issued to Niggemann, and U.S. Pat. No. 5,031,693 issued to Van Dyke, all disclose impingement of coolant, and are all owned by the assignee of the instant application.
Niggemann, et al., U.S. Pat. No. 4,697,427 discloses a cooling apparatus which is adapted for operation in low gravity or high gravity conditions. The device uses a spiral shaped coolant conduit to transfer heat from a heat producing component. An evaporative coolant medium is introduced as a liquid into one end of the conduit. The coolant travels through the conduit, is evaporated by the transfer of heat from the heat load, and is evacuated as a vapor from the other end of the conduit. The flow of coolant through the spiral shaped conduit forces the liquid phase coolant radially outwardly, thus causing the coolant to impinge against the spiraling outer interior wall of the conduit. Vortices generated by flowing vapor phase coolant circulate the liquid phase along the entirety of the inner wall of the conduit to wet the wall and thereby maximize the efficiency of the evaporation.
Other patents disclosing the use of spiral shaped passages in a cooling body include U.S. Pat. No. 4,614,227 issued to Vogel and U.S. Pat. No. 5,034,688 issued to Moulene.
High power density inverters and other power electronics devices are essential elements in aircraft or spacecraft having numerous electrical systems. As such electrical devices become more advanced they typically produce greater amounts of heat. Consequently, such devices require coolers capable of dissipating high intensity heat loads on the order of 100 watts per square centimeter. Absorbing such high intensity heat loads with minimal temperature drop between the power device or component and the coolant can be effected using known liquid coolers. However, a continuing need exists for an efficient and cost-effective cooling device for dissipating the very high thermal loads produced by many electronic components, using a two-phase, evaporative coolant rather than a single-phase liquid coolant. Indeed, when the electronic component is a power converter in a vapor cycle compressor motor drive, two-phase coolant is readily available for cooling purposes.